The present invention relates generally to video displays and in particular the present invention relates to bit rate control over a region of interest of a video display.
The use of video images has become commonplace in recent years. For example, video images are commonly used in security surveillance. In addition, video teleconferencing has enjoyed widespread acceptance in both business and private settings. Video images, as with any type of imagery, provide a picture of multiple objects in a video frame. Sometimes, one object, or a region of the video frame which contains certain objects, is considered more interesting to a viewer than the rest of the video frame. As such, more data bits may be devoted to the coding of this region of the video frame to provide a better overall visual experience. Usually, a region of interest is a dominant foreground object, such as the face of a person provided in the video image.
Because a video image typically contains a fixed amount of data bits, the visual quality of the foreground object is achieved at the expense of the background quality. That is, with a fixed data bandwidth, increasing the quality of one region of a video image decreases the quality of other regions of the video image. Balancing the quality differential between regions of the video image is difficult when the content and data rate of a video image change. There are occasions when a background image is of no interest to a viewer, and the highest quality of a foreground image is desired at the expense of a blurry background image. In contrast, there are occasions when a background image is as important as the foreground image, and it is desirable not to decrease the quality of the background image.
Video data is often compressed using a compression/decompression algorithm (codec) by a bit rate controller. The codec compresses all of the video image data contained in each video frame into a predetermined number of bits. That is, the video image is quantized using the predetermined number of bits. Conventional flat frame encoding uses only one quantization level. In video applications where a region of interest has been identified in a video image, the codec allocates a greater number of the available bits to data provided in the region of interest. The controller uses two quantization levels, one for the region of interest and another for the background region. The quantization level differential between a region of interest and the background of a video frame is typically static and remains constant during a video stream communication. Thus, a viewer cannot adjust the quality of regions of a video image in real-time.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a method of real-time adjusting the quality of regions of a video image.
In one embodiment, a video system comprises a video camera for capturing a video image represented by a first plurality of data bits, and a video compression device coupled to receive the video image from the video camera. The video compression device compresses the first plurality of data bits into a second plurality of data bits. A video compression controller is coupled to the video compression device for selecting a first and second quantization level for use in compressing the first plurality of data bits. The first quantization level is used to compress a first region of the video image and the second quantization level is used to compress a second region of the video image.